Highly scalable and distributed call/media modeling and control framework

ABSTRACT

A highly scalable and distributed call/media modeling and control framework is described. In particular, a plurality of anchor point servers are provided which enable one or more applications to exert call and media control over in-progress communication sessions even though the applications were not originally bound to the communication session during its setup.

FIELD OF THE DISCLOSURE

The present disclosure is generally directed toward communications andmore specifically call modeling and control frameworks.

BACKGROUND

Computer telephony integration, also called Computer-TelephoneIntegration (CTI), is technology that allows interactions on a telephoneand a computer to be integrated or coordinated. As contact channels haveexpanded from voice to include email, web, and fax, the definition ofCTI has expanded to include the integration of all customer contactchannels (voice, email, web, fax, etc.) with computer systems.

Traditional CTI systems provide a very useful logical call model andcontrol mechanism, but they have several important shortcomings. As oneexample, existing CTI systems are typically tied to a specific PrivateBranch eXchange (PBX) and are, therefore, constrained by the domain ofusers/endpoints that PBX is responsible for. It is also difficult todesign a geo-redundant solution due to the tight binding of the CTIsystem to a PBX. It is also difficult to achieve large scale solutions(e.g., support thousands of communication endpoints/users) with a singlePBX. Furthermore, if multiple PBXs are networked together for scale orgeographic distribution, it is difficult to construct a complete modelof a call spanning multiple PBXs. Still further, very few if any CTIsystems provide innate media control mechanisms. Most require anapplication media endpoint to be explicitly added to a call as a thirdparty. Finally, in terms of high availability, most CTI systems arelimited by the availability that is provided by the PBX.

SUMMARY

It is with respect to the above issues and other problems that theembodiments presented herein were contemplated. This disclosureproposes, among other things, mechanisms which allow the creation of acohesive application enablement session monitoring and/or controlsystem.

In some embodiments, through the power of anchor point servers, calls toand/or from users will be sequenced to one or more anchor point serversthat are potentially distributed across geo-regions. Each user willgenerally have at least a primary anchor point server and secondaryanchor point server assigned to them at the Session Initiation Protocol(SIP) sequencing level. When a user makes or receives a call, theiranchor point server (whether primary, secondary, tertiary, etc.) issequenced and an anchor point is established. Once established, theanchor point constructs a logical call model of the participants on thatcall. In some embodiments, each participant in a call will have anestablished anchor point, each of which independently models the callfor that participant.

Additional details related to anchor point servers, anchor points,construction of logical call models with anchor points, and the like aredescribed in U.S. patent application Ser. Nos. 12/783,224 and12/783,249, both of which are hereby incorporated herein by reference intheir entirety.

In some embodiments, in the event of a conference call, an applicationwill see that the far end entity includes a parameter indicating that itis a conference focus (e.g. the isfocus parameter in SIP). Theapplication can then subscribe to conference state events for thatconference focus and thereby construct a complete roster list for thecall. Each anchor point will independently subscribe for call stateevents and maintain its own complete roster list in the call. In theevent of a cascaded conference (i.e., dumbell conference) the anchorpoint will see that one of the conference participants is itself a focusand will then go subscribe to that focus.

One aspect of the present disclosure provides a unified CommunicationSession ID (CSID). In some embodiments, the CSID is the same across allanchor point servers for users that are communicating in the samesession with each other. For two party calls this is relatively easy toaccomplish as it can be a header that is included in the call signalingand which is not modified by intermediate entities (e.g. aP-Charging-Vector ICID for SIP). For conference calls, this becomes abit more complex. When a two party call is escalated to a conferencecall, applications will be notified of a new CSID that represents theconference call (e.g., a conference Uniform Resource Identifier (URI) inSIP). However, older CSIDs will also be correlated with the conferencecall such that applications can continue to issue requests for thatCSID.

In some embodiments, a first end of the anchor point server may comprisea call modeling, call control, and media control remote interface. Theremote interface may be configured to expose the anchor point server toone or more applications. The remote interface could take many formsincluding SOAP web services, REST web services, Bayeux, XML over TCP,etc. The application will leverage a client-side library that willhandle protocol details as well as handle the mapping of users to anchorpoint servers. The client-side library will generally have at least twoanchor point servers provisioned as its first point of contact into thecommunication system. When an application issues a request, it mostoften does so in the context of a user either initiating a call from anendpoint or taking some action on an established SIP dialog.

If a library does not yet have a mapping of the given user to theiranchor point server(s), it will try to send the request to a first pointof contact (i.e., a first anchor point server) and get a redirect if thefirst point of contact is not authoritative for the user. That anchorpoint server will respond with the primary, secondary, tertiary (etc)nodes for that user and the library will store those mappings. In someembodiments, all of this happens transparently to the application.

Once the library has the mapping of a user to their anchor point serverit will send any call creating requests to that user's primary anchorpoint server (if active). If the primary anchor point server is notactive, the request will be sent to the secondary, etc.

One special case that must be considered is that where an application issubscribing for communication events for a given user. In that case, twopossibilities exist to handle the active-active redundancy.

In a first possibility, the client-side library could broadcast thesubscription to all of the user's primary and backup anchor pointservers so that they will able to send events to that application and/orclient-side library should any SIP messages be routed to them by theinfrastructure. In the event of a failure of an anchor point server, theclient-side library would automatically re-subscribe when that anchorpoint server recovers.

In a second possibility, the library could send the subscription only tothe primary anchor point server (or highest ranked active server) andthat subscription would be part of the minimal shared state betweenanchor point servers. In this case, no re-subscription by theclient-side library would be necessary after an anchor point serverrecovers.

In a subset of the cases, rather than a request being issued in thecontext of a user, it will be issued in the context of a CSID (e.g.,query for all participants in a call or add a user to a call). In thesecases, the request is still directed to an anchor point server that hasan anchor point and call model for that CSID. If the request isinitially directed to an anchor point server which hasn't modeled thatCSID, the initially-contacted anchor point server will query all otheranchor point servers to discover which one owns that CSID and willredirect the application to that anchor point server. This prevents theanchor point servers from having to share any per-call data on anongoing basis and will maintain adequate performance since the use ofthese sorts of requests will generally be limited. Alternatively, theidentity of an active anchor point server on a CSID could be encoded inthe CSID itself. The ideal implementation may be to use both of thesemechanisms: in the event that the encoded anchor point server drops froma call (e.g. transfer), the broadcast query could be the fallbackmechanism.

It should be noted that the solution does not need to depend on anyother call feature servers or PBXs.

In some embodiments, the architecture described herein is for anactive-active high availability model. In this architecture, thesecondary, tertiary, etc. anchor point servers are not idle servers.Rather, they are active for one set of users with unused capacityreserved for failure scenarios for other sets of users.

In some embodiments, a method is provided that generally comprises:

receiving, at an application, a request to utilize one or more featuresoffered by the application with respect to an existing communicationsession of a user or the next communication session involving the user;

transmitting, by the application to one or more anchor point servers, arequest to receive event information about communication sessions fromthe anchor point server; and

establishing a communication link between the application and firstanchor point server such that the application can at least one oftransmit control signals for the communication session via thecommunication link and receive event information about communicationsession via the communication link.

The phrases “at least one”, “one or more”, and “and/or” are open-endedexpressions that are both conjunctive and disjunctive in operation. Forexample, each of the expressions “at least one of A, B and C”, “at leastone of A, B, or C”, “one or more of A, B, and C”, “one or more of A, B,or C” and “A, B, and/or C” means A alone, B alone, C alone, A and Btogether, A and C together, B and C together, or A, B and C together.

The term “a” or “an” entity refers to one or more of that entity. Assuch, the terms “a” (or “an”), “one or more” and “at least one” can beused interchangeably herein. It is also to be noted that the terms“comprising”, “including”, and “having” can be used interchangeably.

The term “automatic” and variations thereof, as used herein, refers toany process or operation done without material human input when theprocess or operation is performed. However, a process or operation canbe automatic, even though performance of the process or operation usesmaterial or immaterial human input, if the input is received beforeperformance of the process or operation. Human input is deemed to bematerial if such input influences how the process or operation will beperformed. Human input that consents to the performance of the processor operation is not deemed to be “material”.

The term “computer-readable medium” as used herein refers to anytangible storage that participates in providing instructions to aprocessor for execution. Such a medium may take many forms, includingbut not limited to, non-volatile media, volatile media, and transmissionmedia. Non-volatile media includes, for example, NVRAM, or magnetic oroptical disks. Volatile media includes dynamic memory, such as mainmemory. Common forms of computer-readable media include, for example, afloppy disk, a flexible disk, hard disk, magnetic tape, or any othermagnetic medium, magneto-optical medium, a CD-ROM, any other opticalmedium, punch cards, paper tape, any other physical medium with patternsof holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, a solid state mediumlike a memory card, any other memory chip or cartridge, or any othermedium from which a computer can read. When the computer-readable mediais configured as a database, it is to be understood that the databasemay be any type of database, such as relational, hierarchical,object-oriented, and/or the like. Accordingly, the disclosure isconsidered to include a tangible storage medium and prior art-recognizedequivalents and successor media, in which the software implementationsof the present disclosure are stored.

The terms “determine”, “calculate”, and “compute,” and variationsthereof, as used herein, are used interchangeably and include any typeof methodology, process, mathematical operation or technique.

The term “module” as used herein refers to any known or later developedhardware, software, firmware, artificial intelligence, fuzzy logic, orcombination of hardware and software that is capable of performing thefunctionality associated with that element. Also, while the disclosureis described in terms of exemplary embodiments, it should be appreciatedthat individual aspects of the disclosure can be separately claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is described in conjunction with the appendedfigures:

FIG. 1 is a block diagram of a communication system in accordance withembodiments of the present disclosure;

FIG. 2 is a block diagram depicting a first configuration ofcommunication system elements in accordance with embodiments of thepresent disclosure;

FIG. 3 is a block diagram depicting a second configuration ofcommunication system elements in accordance with embodiments of thepresent disclosure;

FIG. 4 is a block diagram depicting a configuration of communicationsystem elements to support a communication session between two usersthat share an anchor point server in accordance with embodiments of thepresent disclosure;

FIG. 5 is a block diagram depicting a configuration of communicationsystem elements to support a communication session between two usersthat do not share an anchor point server in accordance with embodimentsof the present disclosure;

FIG. 6 is a block diagram depicting a configuration of communicationsystem elements to support a conference communication session betweenthree or more users in accordance with embodiments of the presentdisclosure;

FIG. 7 is a flow diagram depicting an application-to-anchor point serverbinding process in accordance with embodiments of the presentdisclosure;

FIG. 8 is a call-signaling diagram depicting an application monitoringuser call activity via an anchor point in accordance with embodiments ofthe present disclosure; and

FIG. 9 is a flow diagram depicting a process of utilizing a CSID toenable an application to operate on behalf of multiple users for acommunication session in accordance with embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The disclosure will be illustrated below in conjunction with anexemplary communication system. Although well suited for use with, e.g.,a system using a server(s) and/or database(s), the disclosure is notlimited to use with any particular type of communication system orconfiguration of system elements. Those skilled in the art willrecognize that the disclosed techniques may be used in any communicationapplication in which it is desirable to utilize anchor points.

The exemplary systems and methods of this disclosure will also bedescribed in relation to analysis software, modules, and associatedanalysis hardware. However, to avoid unnecessarily obscuring the presentdisclosure, the following description omits well-known structures,components and devices that may be shown in block diagram form, are wellknown, or are otherwise summarized.

For purposes of explanation, numerous details are set forth in order toprovide a thorough understanding of the present disclosure. It should beappreciated, however, that the present disclosure may be practiced in avariety of ways beyond the specific details set forth herein.

FIG. 1 depicts a communication system 100 according to an embodiment ofthe present disclosure. The communication system 100 may include anenterprise network 104 that is in communication, via a (typicallyun-trusted or unsecure or public) communication network 108, with one ormore external communication devices 112. The external communicationdevices 112 are generally referred to as “external” because they areeither not under the direct control of the enterprise administering theenterprise network 104 or have a decreased level of trust with theenterprise network 104 as compared with communication devices 136 thatare within the enterprise network 104. Exemplary types of externalcommunication devices 112 include, without limitation, cellular phones,laptops, Personal Computers (PCs), Personal Digital Assistants (PDAs),digital phones, analog phones, and the like.

The communication network 108 may be packet-switched and/orcircuit-switched. An exemplary communication network 108 includes,without limitation, a Wide Area Network (WAN), such as the Internet, aPublic Switched Telephone Network (PSTN), a Plain Old Telephone Service(POTS) network, a cellular communications network, or combinationsthereof. In one configuration, the communication network 108 is a publicnetwork supporting the TCP/IP suite of protocols.

The enterprise network 104 may include a boundary device 116 including aserver table 120, a communication server 124 including a call featuresequencer 128 and a user table 132, one or more internal communicationdevices 136, an anchor point server 140, one or more application servers144 which may be capable of providing one application 148 or a set ofdifferent applications 152, a number of other servers 156, and anenterprise database 160, all of which are interconnected by a (trustedor secure or private) Local Area Network (LAN) 164. Some or all of thefunctions depicted in FIG. 1 may be co-hosted and/or co-resident on asingle server. The depiction of components in FIG. 1 is generallyintended to be a logical depiction of the components of the system 100.

The LAN 164 can be secured from intrusion by untrusted parties by agateway and/or firewall located between the LAN 164 and communicationnetwork 108. In some embodiments the boundary device 116 may include thefunctionality of the gateway and/or firewall. In some embodiments, aseparate gateway or firewall may be provided between the boundary device116 and the communication network 108.

The communications server 124 can include a Private Branch eXchange(PBX), an enterprise switch, an enterprise server, combinations thereof,or other type of telecommunications system switch or server. Thecommunication server 124 is preferably configured to executetelecommunication functions such as the suite of or Avaya Aura™applications of Avaya, Inc., including Communication Manager™, AvayaAura Communication Manager™, Avaya IP Office™, Communication ManagerBranch™, Session Manager™, System Manager™, MultiVantage Express™, andcombinations thereof.

Although only a single communications server 124 is depicted in FIG. 1,two or more communications servers 124 may be provided in a singleenterprise network 104 or across multiple separate LANs 164 owned andoperated by a single enterprise, but separated by a communicationnetwork 108. In configurations where an enterprise or an enterprisenetwork 104 includes two or more communications servers 124, each server124 may comprise similar functionality, but may be provisioned forproviding its features to only a subset of all enterprise users. Inparticular, a first communications server 124 may be authoritative forand service a first subset of enterprise users whereas a secondcommunications server 124 may be authoritative for and service a secondsubset of enterprise users, where the first and second subsets of usersgenerally do not share a common user. This is one reason why the networkboundary device 116 may be provided with a server table 120. The samemay be true of the anchor point server 140.

Additionally, multiple servers 124 can support a common user community.For example, in geo-redundant and other applications where users aren'tnecessarily bound to a single application server, there may be a clusterof equivalent servers where a user can be serviced by any server in thecluster.

In accordance with at least some embodiments of the present invention,the mapping of user identities within a communication request does notnecessarily have to occur at the network boundary device 116. Forinstance, the mapping between an authoritative server and a user mayoccur “behind” the network boundary device 116 within the enterprisenetwork 104.

In some embodiments, network boundary device 116 is responsible forinitially routing communications within the enterprise network 104 tothe communications server 124 responsible for servicing a particularuser involved in the communication. For example, if a first enterpriseuser is being called by an external communication device 112, then thenetwork boundary device 116 may initially receive the inbound call,determine that the call is directed toward the first enterprise user,reference the server table 120 to identify the authoritativecommunications server 124 for the first enterprise user, and route theinbound call to the authoritative communications server 124. Likewise,communications between internal enterprise users (e.g., internalcommunication devices 136) may first be serviced by the originatinguser's authoritative communications server 124 during the originationphase of communications set-up. After the origination phase is complete,the authoritative communications server 124 of the terminating (orcalled) user may be invoked to complete the termination phase ofcommunications set-up. In some embodiments, the communications server124 for the originating and terminating user may be the same, but thisis not necessarily required. In situations where more than twoenterprise users are involved in a communication session, authoritativecommunications servers 124 for each of the involved users may beemployed without departing from the scope of the present invention.Additionally, the authoritative communications servers 124 for each usermay be in the same enterprise network 104 or in different enterprisenetworks 104, which are owned by a common enterprise but are separatedby the communication network 108.

Each communications server 124 includes a feature sequencer 128 and auser table 132. The user table 132 for a communications server 124contains the communication preferences for each user for which it isauthoritative. In particular, the user table 132 may be provisioned byusers and/or by administrative personnel. The communications preferencesfor a particular user are referenced by the feature sequencer 128 todetermine which, if any, features (i.e., applications 148, 152) shouldbe incorporated into a communication session for the user. The featuresequencer 128 can actually provide communication features directly intothe communication session or the feature sequencer 128 can determine anapplication sequence which will be invoked during set-up and used duringthe communication session.

In accordance with at least some embodiments, the feature sequencer 128can determine an application sequence and cause one or more applications148, 152 to be sequenced into a communication session. In particular,the feature sequencer 128 is configured to analyze a particular user'scommunication preferences and invoke the necessary applications tofulfill such preferences. Once an application sequence is determined bythe feature sequencer 128, the communications server 124 passes thecommunication-establishing message to a first application in theapplication sequence, thereby allowing the first application todetermine the parameters of the communication session, insert itselfinto the control and/or media stream of the communication session, andthereby bind itself to the communication session. Once the firstapplication has inserted itself into the communication session, thefirst application either passes the communication-establishing messageback to the feature sequencer 128 to identify the next application inthe application sequence or passes the communication-establishingmessage directly to a second application in the application sequence.Alternatively, or in addition, the message may be redirected, rejected,or the like. Moreover, parties and/or media servers may be added to thecall by an application. As can be appreciated, this process continuesuntil all applications have been included in the communication sessionand the process can be duplicated for each of the users involved in thecommunication session.

In some embodiments, an application 148, 152 is bound to acommunications session through an anchor point server 140. Accordingly,the feature sequencer 128 may initially bind an anchor point server 140into an application sequence during the initial communication sessionsetup. In many cases, the application 148, 152 will subscribe to eventnotifications for a given user before a call is initiated and evenbefore an anchor point server 140 is sequenced into a call sequence. Inother cases, applications 148, 152 may subscribe to event notificationsafter a call is in progress. In either case, applications 148, 152 mayalso leverage the anchor point server 140 to exert control over thecommunication session.

Although only two application servers 144 are depicted, one skilled inthe art will appreciate the one, two, three, or more applicationsservers 144 can be provided and each server may be configured to provideone or more applications. The applications provided by a particularapplication server 144 may vary depending upon the capabilities of theserver 144 and in the event that a particular application server 144comprises a set of applications 152, one, some, or all of theapplications in that set of applications 152 may be included in aparticular application sequence. There is no requirement, however, thatall applications in a set of applications 152 be included in anapplication sequence and there is no requirement as to the order inwhich applications are included in the application sequence. Rather, theapplication sequence is usually determined based on a user'scommunication preferences, which can be found in the user table 132.Alternatively, or in addition, the applications that appear in a userssequence vector and their order within that vector may be determined bya system administrator to satisfy business requirements.

Moreover, the application sequence can vary based on the media type(s)that are being used in the communication session. For instance, a usermay have a first set of preferences for voice-based communications, asecond set of preferences for video-based communications, and a thirdset of preferences for text-based communications. Additionally, a usermay have preferences defining preferred media types and rules forconverting communication sessions from one media type to anotherdifferent media type. Still further, a user may have preferencesdefining the manner in which multi-media communications are establishedand conducted.

The applications included in a particular application sequence aregenerally included to accommodate the user's preferences. Applicationsmay vary according to media-type, function, and the like. Exemplarytypes of applications include, without limitation, an EC-500 (extensionto cellular) application, a call setup application, a voicemailapplication, an email application, a voice application, a videoapplication, a text application, a conferencing application, a callrecording application, a communication log service, a securityapplication, an encryption application, a collaboration application, awhiteboard application, mobility applications, presence applications,media applications, messaging applications, bridging applications, andany other type of application that can supplement or enhancecommunications. Additionally, one, two, three, or more applications of agiven type can be included in a single application sequence withoutdeparting from the scope of the present invention.

In accordance with at least some embodiments of the present disclosure,the anchor point server 140 is provided as a mechanism to create anchorpoints in a user's communication sequence thereby allowing certainapplications 148, 152 to become aware of and control a communicationsession after the session has been established or allow certainapplications 148, 152 to leave a communication session before thesession has ended. Particularly, the anchor point server 140 may bind ananchor point or multiple anchor points to a communication session duringset-up, but may not necessarily bind any media resource to thecommunication session until an application identifies a need for thatmedia resource. Accordingly, the anchor point server 140 may incorporateone or more anchor points into the logical communication sequence beforeand/or after other sequenced applications are bound to the communicationsession.

Prior to the introduction of anchor points, if an application 148, 152wanted to have the ability to exert media control on a givencommunication, it would have to be explicitly provisioned as a sequencedapplication. However, some applications don't really care about thecommunication setup phase: they are content to let the communicationproceed to the originally addressed party and then exert media and callcontrol mid-session. Provisioning such applications as sequencedapplications can often result in an unnecessary waste of media resourcesand an increase in call establishment latency.

In some embodiments, anchor points are not unique to an application.Instead, they are control points that any application may leverage. Theymay not even be provisioned but instead are sequenced in automaticallyby the feature sequencer 128 which would know what anchor points server140 is authoritative for a given user, as this information may also befound in the user table 132. The anchor point provided by an anchorpoint server 140 would always be sequenced into at least one point ofthe application sequence. The location in which the anchor point isplaced may vary depending upon the types of features which are desired.Moreover, multiple anchor points may be inserted into a communicationsession without departing from the scope of the present invention.

The applications that leverage anchor points would be provided with alogical call model similar to that provided by a computer supportedtelephony application (CSTA), Parlay-X, or any other paradigm used tocommunicate call state and operations between an application and ananchor point. Such applications that would potentially want to leveragean anchor point would subscribe to call events for endpoints of interestand would be notified when call/connection status changes for acommunication session. In some embodiments, the anchor points would notbe visible to the applications. Instead, they would invoke mediaoperations on calls or connections within that call and the anchorpoints would be leveraged transparently.

In most cases, an anchor point would not initially involve a mediaresource in the media path (e.g., a Real time Transport Protocol (RTP)path). Instead, the anchor point inserts itself as a Back-to-Back UserAgent (B2BUA) in the signaling path. Only when an application requests amedia action would the anchor point start a Media Server Markup Language(MSML) session with the application server 144 then RE-INVITE to eachside to insert the application server 144 into the RTP path. Inembodiments where the anchor point is located “next-door” to theendpoint, it is always guaranteed to be able to play or recordexclusively to that given endpoint/user. Since it is possible to addanchor points for each user in an enterprise call, per-party mediaoperations would generally be possible regardless of any intermediateconference foci or applications. Since the media resources required toimplement a particular application 148, 152 are not inserted into thepath until it is needed, media resources are not wasted and additionalRTP delay is avoided.

If each anchor point always brought its own media resources this wouldpotentially result in wasted resources and additional RTP delay. This iswhere media tokens may be utilized. The first anchor point to insert afirst media resource (e.g., a media server) will include a media tokenin the header of the INVITE or RE-INVITE that is eventually received bya second anchor point involved in the same communication session. Thisother anchor point will, in most cases, then use the media tokeninformation to leverage the media server inserted by the first anchorpoint, if possible. However, if an intermediate application orconference focus has inserted its own media resources, this mediaresource reuse by the other anchor point could result in the sameproblem as before with an application thinking that it is playing orrecording one party but really getting multiple parties. To get aroundthis problem the second anchor point will compare the SessionDescription Protocol (SDP) information in the media token with the SDPinformation it received in the RE-INVITE. If the SDP attributes match,there is no intermediate media server and the first media resource maybe reused. If they do not match, then a new media resource is introducedfor the second application. Additional descriptions of media tokens andthe advantages of using the same are provided in U.S. patent applicationSer. No. 12/574,604 to Braudes et al. filed Oct. 6, 2009, the entirecontents of which are hereby incorporated herein by reference.

One feature that can be supported is that an application can tell theanchor point that it should always include a particular media resourcefor all calls for a given user (i.e., based on user preferences in theuser table 132). An example would be if the application knows that italways wants to record all calls for a given user. In that case, theapplication would indicate this to the anchor point (perhaps with aparameter when establishing a monitor for that user) and, therefore, thepotential for “clipping”, which would be otherwise introduced byinserting a new media resource mid-call, would be eliminated.

However, it is often the case that applications 148, 152 won't specify amedia resource to be used, but instead will generically ask for a mediaresource to be included in a communication session. Upon receiving sucha request from an application 148, 152, an anchor point server 140 willselect an appropriate resource for the application 148, 152 and invokethe selected resource.

In some embodiments, these anchor points could also potentially be usedfor call control purposes, being a B2BUA. They would enable transfer,conference, drop operations on behalf of another controlling entity.

The other servers 156 may comprise email servers, voicemail servers,calendaring servers, conferencing servers, and other types of serversknown to provide particular services to client devices. In someembodiments, the other servers 156 may also be considered applicationservers 144, which provide one or more applications for use in acommunication session.

The internal communication devices 136 can be similar or identical tothe external communication devices 112, except they are provisioned, andoften owned, by the enterprise. Exemplary types of communication devices112 include, without limitation, any capable phone, hardphone, softphoneand/or digital telephone. Examples of suitable telephones include the1600™, 2400™, 4600™, 5400™, 5600™, 9600™, 9620™, 9630™, 9640™, 9640G™,9650™, and Quick Edition™ telephones, IP wireless telephones (such asAvaya Inc.'s IP DECT™ phones), video phones (such as Avaya Inc.'sVideophone™), and softphones of Avaya, Inc.

The enterprise database 160 includes enterprise subscriber information,such as name, job title, electronic address information (e.g., telephonenumber, email address, instant messaging handle, direct dial extension,and the like), subscriber contact lists (e.g., contact name andelectronic address information), other employee records, and the like.

With reference now to FIG. 2, a configuration of a communication system200 in which an application 208 leverages an anchor point server 216 toparticipate in a communication session will be described in accordancewith at least some embodiments of the present disclosure. Thecommunication system 200 configuration represents a redundant orhighly-available set of anchor point servers 216 a-N which provide oneor more anchor points in a communication session for an application 208.The application server 204 may be similar or identical to theapplication server 144. The anchor point servers 216 a-N may be similaror identical to the anchor point server 140. In some embodiments, theanchor point servers 216 a-N may be co-located in a common facility ormay be physically separated from one another to provide geo-redundancy.For example, the anchor point servers 216 a-N may be separated by one ormore geographical boundaries or borders such as state lines, countrylines, oceans, etc. The feature sequencer 224 may be similar oridentical to the feature sequencer 128 provided on the communicationserver 124 or it may be a stand-alone component. In some instances, thefeature sequencer 224 may be geo-redundant, meaning that multipleversions of the feature sequencer 224 are provided at separate physicallocations, possibly at different LANs in a larger WAN.

In some embodiments, the application server 204 provides one or severalapplications 208 as well as one or more client libraries 212. The clientlibrary 212 is a set of instructions that are application-independent,meaning that the client library 212 can serve a plurality ofapplications 208. In some embodiments, the client library 212 isprovided to manage mappings of users to anchor point servers so that anyapplication, including application 208, can leverage the client library212 to attach to an anchor point established by an anchor point server.This allows the application 208 to be unaware of how many anchor pointservers 140 are actually in existence as well as any mappings associatedwith such anchor point servers 140. Rather, this task is delegated tothe client library 212 and made available to the application 208 on aper-request basis.

More specifically, the client library 212 may contain a listing ofusers, user IDs, Addresses of Record (AoRs), user aliases, etc. that aremapped to one or more anchor point servers 216 a-N. In some embodiments,the client library 212 also includes instructions for keeping track ofwhich server is primary/secondary/tertiary for particular users, but itdoesn't have to indicate any of that information to any other component.Rather, it directly uses that information to respond to requestsreceived from applications. In some embodiments, the client library 212maintains information that indicates which of the anchor point servers216 a-N is a primary anchor point server for a user (i.e., anchor pointserver to be used as a default for a user if available), which of theanchor point servers 216 a-N is a secondary anchor point server for auser (i.e., anchor point server to be used if the primary anchor pointserver is unavailable), which of the anchor point servers 216 a-N is atertiary anchor point server for a user (i.e., anchor point server to beused if the primary and second anchor point servers are unavailable),and so on.

Likewise, each anchor point server 216 a-N may maintain lists of itsprimary users 220 a and lists of secondary users 220 b. The lists 220 a,220 b may identify which users the anchor point server 216 supports. Ifa particular anchor point server 216 is not authoritative for aparticular user or group of users, then the lists 220 a, 220 b may alsoidentify which anchor point servers 216 are authoritative for aparticular user or group of users. Thus, the client library 212 can, onbehalf of an application 208, query any one of the anchor point servers216 and determine which anchor point server 216 is authoritative for aspecific user. Once the client library 212 obtains such information fromthe anchor point server 216, the client library 212 can update itsinternal records of user-to-anchor point server mapping and make suchinformation available to applications on an as-needed basis.

As discussed above, the feature sequencer 224 may initially sequence oneor more anchor point servers 216 a-N into an application sequence duringcall initialization. In some embodiments, an application 208 may beconfigured to monitor all communication sessions for a given user rightfrom the start of the communication session and it may utilize an anchorpoint server 216 a-N to accomplish such monitoring. In otherembodiments, at some point after the communication session has begun, auser may invoke the application 208 to begin monitoring thecommunication session. Upon being invoked, the application 208 may firstrefer to the client library 212 to determine if an authoritative anchorpoint server 216 a-N is already known for that user. If so, the clientlibrary 212 returns the mapping information to the application 208 orroutes the application's 208 request to the appropriate anchor pointserver 216 on behalf of the application such that the application 208 isenabled to issue a call monitoring/control request to the identifiedanchor point server 216. If, however, the client library 212 does nothave an anchor point server entry for the user, then the client library212 sends a request to either a default anchor point server 216 orrandomly selected anchor point server 216. If that server happens to beauthoritative for that user, then the anchor point server 216 willprocess the request in the normal fashion thereby binding theapplication 208 to a particular communication session. If the queriedserver is not authoritative for that user, then the server 216 maysimply refer to its internal lists 220 a, 220 b to identify which of theanchor point servers 216 a-N is authoritative for the user and providethat information back to the application 208.

The provision of multiple anchor point servers 216 a-N enables ahighly-available configuration of anchor points. In some embodiments,the anchor point servers 216 a-N may be configured in an active-passiveconfiguration where one anchor point server 216 operates as a primaryanchor point server for a user whereas another anchor point server 216operates as a secondary anchor point server. In the active-passiveconfiguration, the primary anchor point server 216 may be invoked by thefeature sequencer, receive the media stream of the communicationsession, and perform all functions required to create an anchor pointand enable the application 208 to leverage the anchor point. Thesecondary anchor point server 216, on the other hand, may remain idleuntil it is detected that the primary anchor point server 216 is nolonger capable of providing the necessary functions (i.e., the primaryanchor point server 216 has failed). If such an event is detected, thenfailover procedures may be followed whereby some per-call stateinformation is shared between anchor point servers 216 of aninter-anchor point communication link 232 a, 232 b. The call stateinformation enables the secondary anchor point server 216 to continueoffering the application 208 a means for connecting to the communicationsession, receiving call-based event notifications, and exerting controlover media of the communication session.

As an alternative to the active-passive configuration, redundant anchorpoint servers 216 may be set up as active-active. This configurationmeans that multiple anchor point servers 216 may be active for a singleuser during a communication session. Only one of the anchor pointservers 216 may be used by the application 208 and the other anchorpoint server 216 may simply store the call event information withoutfurther processing. The active-active configuration enables a quickerand smoother transition during failover. The utilization of anactive-active configuration also avoids the need to tear down acommunication session during failover and failback. If call preservationduring failover is a goal, then call state sharing may be required sinceonly the primary anchor point server would be initially sequenced.

In some embodiments, the client library 212 could issue subscriptionsfor a given user to each of the anchor point servers 216 that mightbecome authoritative for that given user. In that case, the anchor pointservers 216 wouldn't have to share state with each other with respect toapplication subscriptions. However, other call state may have to beshared.

In some embodiments, the anchor point servers 216 a-N are configured toalways and only see two legs of a communication session. The two primarycases are a two-party conversation or a conference call where the secondleg seen by an anchor point server 216 is to a conference focus. Whatenables the application 208 to see a centralized communication session(similar to a PBX-based communication session) is the anchor pointserver 216 composes a logical call model. It also allows the anchorpoint servers 216 to hide from the applications 208 whether or not theyare involved in a two-party call or a conference call.

As can be seen in FIG. 2, a first communication link 228 a, 228 b, 228Nmay be established between the application server 204 and anchor pointserver 216 a, 216 b, 216N, respectively. The first communication link228 a, 228 b, 228N may be used to exchange call event information andbinding requests for specific groups of users. In some embodiments, eachanchor point server 216 may be provided with a remote interface thatfacilitates the establishment and maintenance of the first communicationlink 228 a, 228 b, 228N. Remote interface may comprise a call modeling,call control, and media control remote interface that exposes the anchorpoint server 216 to the application server 204. This remote interfacecan take many forms including, without limitation, SOAP web services,REST web services, Bayeux, XML over TCP, and so on.

A second communication link 236 a, 236 b, 236N may also be establishedbetween the feature sequencer 224 and anchor point server 216 a, 216 b,216N, respectively. The second communication link 236 a, 236 b, 236N maybe used to carry session signaling between on behalf of the application208 to/from the communication session. The second communication link 236a, 236 b, 236N provides the application 208 with a mechanism forreceiving call state information and exerting control over mediaresources of the communication session.

As can be seen in FIG. 3, a situation may occur where one or more of theanchor point servers 216 become either temporarily or permanentlyunavailable. This situation is usually referred to as a server failureand may result in the need to perform failover procedures for users thatwere leveraging the now failed anchor point server 216. As discussedabove, the steps taken during failover may depend upon whether anactive-passive or active-active model is being followed by the anchorpoint servers 216 a-N. In an active-passive model, some call-stateinformation may need to be provided to the backup anchor point server216 before the application 208 is enabled to utilize an anchor pointprovided by the anchor point server 216. In an active-active model, auser's secondary anchor point server 216 is not idle. Rather, it isactive for all users in its secondary list of users 220 b with unusedcapacity reserved for failure scenarios.

In the event of a failure, the possibility exists that there will be atransitory state where multiple anchor point servers 216 a-N have activecalls for a given user. In this case, any mid-call requests (e.g., holdcall, retrieve call, etc.) should be directed by the client library 212to the anchor point server 216 that owns the call (i.e., isauthoritative for the user initiating the request). This can beaccomplished by encoding an ID of the anchor point server 216 hashandled the call up until failure was detected into a connection ID thatis used by the application 208 to perform the mid-call request. In someembodiments, the connection ID may comprise a combination of the CSIDfor a particular call, a user ID (identifying the requesting user), andan identification of the anchor point server 216 which is requested toperform the action on behalf of the user.

With reference now to FIG. 4, a configuration of communication systemelements to support a communication session between two users that sharean anchor point server is shown in accordance with embodiments of thepresent disclosure. It may be the case that two users involved in acommunication session share the same anchor point server 216 as theirprimary anchor point server 216. In some embodiments, an anchor pointserver 216 will model a call twice, once for each user. In such aconfiguration, a single first communication link 228 is establishedbetween the application server 204 and anchor point server 216 and asingle second communication link 236 is established between the featuresequencer 224 and anchor point server 216. Third communication links 412a, 412 b may be established between the feature sequencer 224 and eachendpoint 404 a, 404 b involved in the communication session. The thirdcommunication links 412 a, 412 b may carry session signaling for aparticular user or endpoint. Accordingly, session signaling for user Amay be carried by communication link 412 a whereas session signaling foruser B may be carried by communication link 412 b. Anendpoint-to-endpoint link 408 may also be established between theendpoints 404 a, 404 b to carry media between the endpoints 404 a, 404b, thereby facilitating the communication session between the endpoints404 a, 404 b. In some embodiments, the endpoint-to-endpoint link 408 isan RTP or SRTP stream.

With reference now to FIG. 5, an alternative configuration ofcommunication system elements to support a communication session betweentwo users that do not share an anchor point server is shown inaccordance with embodiments of the present disclosure. Here, a firstanchor point server 216 a is authoritative for user A and a secondanchor point server 216 b is authoritative for user B. There is norequirement to share per-call state data between the anchor pointservers 216 a, 216 b. Each anchor point server 216 a, 216 b enables theapplication 208 to provide the desired features for both users, butstill enables the application to maintain a single logical view of thecall.

As compared to the configuration of FIG. 4, there are multiple firstcommunication links 228 a, 228 b and second communication links 236 a,236 b. The communication link 228 a between the application server 204and first anchor point server 216 a carries event and request datasignals for user A. Likewise, the communication link 228 b between theapplication server 204 and the second anchor point server 216 b carriesevent and request data signals for user B. User A's session signaling iscarried over communication links 236 a and 412 a. User B's sessionsignaling is carried over communication links 236 b and 412 b.

With reference now to FIG. 6, a configuration of communication systemelements to support a conference communication session between three ormore users is depicted in accordance with embodiments of the presentdisclosure. As with the configuration of FIG. 5, there is no requirementthat per-call state information is shared between the anchor pointservers 216 a and 216 b. Also, the configuration depicted in FIG. 6shows that one anchor point server (e.g., second anchor point server 216b) is authoritative for two users involved in the conference (e.g., userB and user C). It may be the case that all of the users share the sameanchor point server 216 as their primary server or it may be the casethat each user has a different anchor point server 216 as theirauthoritative anchor point server. The example depicted in FIG. 6 isprovided for explanation purposes only and is not intended to limit thescope of the present disclosure.

In a conference communication session, a conference focus 604 may beintroduced as a point where media is shared, mixed, and re-distributedamong the endpoints 404 a, 404 b, 404 c. In some embodiments, theconference focus 604 may comprise a conference bridge or conferencemixer residing on a conferencing server. Alternatively, the conferencefocus 604 may reside at one of the endpoints 404 a, 404 b, 404 c.

In this embodiment, media is exchanged between the endpoints 404 a, 404b, 404 c via the conference focus 604 and the media signals are carriedover communication links 612 a, 612 b, 612 c. In some embodiments, thecommunication links 612 a, 612 b, 612 c may correspond to RTP or SRTPstreams that have been established using SIP or some other similarprotocol.

Additional communication links 608 a and 608 b may be establishedbetween the conference focus 604 and anchor point servers 216 a and 216b, respectively. The communication links 608 a, 608 b may be used by theanchor point servers 216 a, 216 b to subscribe to conference stateevents and receive information about such events directly from theconference focus 604 rather than through the endpoints 404 a, 404 b, 404c and feature sequencer 224. This enables each anchor point server 216a, 216 b to maintain an awareness of activity at the conference focus.Thus, if another user joins the conference via an endpoint alreadyinvolved in the conference, the conference focus 604 will become awareof the addition of the new user and will send a state event to theanchor point servers 216 a, 216 b indicating the same.

In some embodiments, the anchor point servers 216 a, 216 b uses theconference events to compose a complete roster list even though theanchor points for the individual users are spread across N servers.There could also be N conference foci in a highly scalable, highlydistributed network and the logical call model abstracts the applicationfrom that information.

With reference now to FIG. 7, an application binding process will bedescribed in accordance with at least some embodiments of the presentdisclosure. The method begins when a feature sequencer 224 or userinvokes an application 208 to begin the application binding processwhereby the application attempts to bind itself to a communicationsession (step 704). In some embodiments, the communication session maybe an in-progress communication session whereas in other embodiments theapplication may be bound to a communication session via an anchor pointserver 216 when the anchor point server 216 is initially sequenced intothe communication session. Upon receiving the instructions to start thebinding process, the application 208 issues a monitor request for callsto/from a particular user (step 708). The request is received at aclient library 212 and the client library 212 refers to itslocally-maintained data structures to determine if it already knows theauthoritative (i.e., primary) anchor point server 216 for the particularuser (step 712).

If an entry is found in the client library 212 for the particular user,then the client library 212 may identify the anchor point server 216which is mapped to the particular user in its data structures (step 716)and issue a request to the anchor point server 216 identified as theprimary anchor point server 216 on behalf of the application 208 (step724). Thus, a client library 212 is enabled to create anapplication-to-anchor point binding on behalf of one or manyapplications.

In some embodiments where an active-active configuration of anchor pointservers 216 is used, the client library 212 may issue multiple requeststo multiple anchor point servers 216. The issuance of multiple requestsmay be done by broadcasting the request to all known anchor pointservers 216 or by transmitting the request to selected ones of theanchor point servers 216. It should be noted, however, that broadcastingof multiple requests can be done in situations where the request is aquery or a subscription and can generally not be done if the request isfor call control.

Alternatively, if there is no entry in the client library 212, then theclient library 212 selects an anchor point server 216 either by defaultselection rules or by random and acts as if that selected anchor pointserver 216 is actually the primary anchor point server 216 for therequesting user (step 720). The selection of a single anchor pointserver 216 may occur regardless of whether an active-active oractive-passive mode of anchor point server operation is utilized.

Once an anchor point server 216 has been identified by the application208, either via the client library 212 or via a selection algorithm, themethod continues with the client library 212 issuing a request on behalfof the application 208 to the selected anchor point server 216 (step724). The request(s) issued to the anchor point server(s) 216 containsinstructions for the anchor point server 216 to utilize an anchor pointestablished or soon to be established in a particular communicationsession (in which the particular user may or may not already be aparticipant) to retrieve call event, control, and other data and providesuch data back to the application 208. The anchor point will also beused by the application 208 to exert call control and media control overthe communication session via control signals transmitted to the anchorpoint server 216 that has established the anchor point. The request mayalso contain one or more of a user ID, an AoR, an alias, a CSID, or anyother identification of a user or communication session that enables theanchor point server 216 to determine if it is configured and/or allowedto support the request issued by the application 208.

Upon receiving the request from the application 208, the anchor pointserver 216 refers to its internally-maintained lists 220 a, 220 b todetermine if it is actually the anchor point server 216 that isauthoritative for the requesting user (step 728). This step may beperformed by each of the anchor point servers 216 that receives therequest from the application 208 (i.e., if multiple requests weretransmitted or broadcast to multiple anchor point servers 216). In thisstep, the anchor point server 216 will search for either a useridentifier in its internally-maintained list 220 a, 220 b or it willsearch for a CSID contained in the request. If the request transmittedby the application 208 contained a CSID, then the anchor point server216 will determine if it currently has an anchor point established in acommunication session that has been assigned the CSID contained in therequest.

If the analysis of the request indicates that the anchor point server216 is not authoritative for the requesting user (or there is no CSIDmatch), then the anchor point server 216 may either attempt to identifyan alternative anchor point server 216 as the appropriate server tohandle the request and may transmit such information back to therequesting application 208 (step 732). Alternatively, if the anchorpoint server 216 does not know the identity of the appropriate anchorpoint server 216 to handle the request, the anchor point server 216 mayrespond to the application 208 that it is not capable of supporting therequest or it may not respond at all. This may initiate a process wherethe application 208 attempts to identify an alternative anchor pointserver 216 and issues a request to that anchor point server 216 untilthe authoritative anchor point server 216 for the requesting user isfound.

If the anchor point server 216 analyzes the request and determines thatit is authoritative for the requesting user (either as a primary orsecondary anchor point server), then the anchor point server 216 maysend a response to the application 208 indicating the same. Uponreceiving the affirmative response from the anchor point server 216, theclient library 212 may update its locally-maintained data structures bymapping either a user ID, the CSID, or some other identifier to anidentifier of the anchor point server 216 that has affirmativelyresponded to the request (step 736).

Once the client library 212 has been updated with the user-to-anchorpoint server mapping information, the method continues with theapplication 208 using the anchor point established by the authoritativeanchor point server 216 to exert control over the call and receive callevent and status information (step 740).

Although FIG. 7 depicts the application 208 as issuing a monitoringrequest before identifying communication sessions, embodiments of thepresent disclosure also contemplate situations where the application 208may first issue a query for all existing sessions for a particular user.The query may be transmitted to one or more anchor point servers 216 viathe client library 212. If the application 208 learns of an in-progresscommunication session for the particular user, then the application 208may attempt to bind itself to that communication session (if it isn'talready bound to that communication session) and then attempt to take anaction on that in-progress communication session.

FIG. 8 depicts a signaling sequence used by the application 208 toestablish, before or after a communication session begins, acall-monitoring function for a particular user in accordance with atleast some embodiments of the present disclosure. As with otherembodiments described herein, the application 208 has access to a clientlibrary 212 that maintains one or more data structures for mapping usersto anchor point servers 216. In the embodiment depicted in FIG. 8, UserA is mapped to the first anchor point server 216 a (i.e., the firstanchor point server 216 a is authoritative for User A) and User B ismapped to the second anchor point server 216 b (i.e., the second anchorpoint server 216 b is authoritative for User B).

The sequence begins when the application 208 determines that it wants tomonitor all communication sessions (i.e., those not yet established andthose already in progress) for one or more users. In the exampledepicted in FIG. 8, the application 208 determines that it wants tomonitor communication sessions for Users A and B. As can be appreciated,however, the application 208 may only be interested in monitoringcommunication sessions for User A or User B, but not both. In such asituation, the application 208 will issue a single atomic monitorrequest to one of anchor point servers 216 a, 216 b rather than issuingtwo unrelated requests to both anchor point servers 216 a, 216 b as willbe described in further detail herein.

This determination may be made in response to the application 208receiving a user input requesting to monitor all calls for Users A and Bor it may be made automatically in response to a pre-provisioned rulethat dictates the application 208 is to be invoked for communicationsessions in which Users A and B are involved. In some embodiments, thisdetermination is made once when the application 208 starts up (i.e., ispowered up). Upon making this determination, the application 208 issuesa request to the client library 212 which identifies the first anchorpoint server 216 a as authoritative for User A and the second anchorpoint server 216 b as authoritative for User B and forwards the requeststo the first and second anchor point servers 216 a, 216 b for User A andUser B, respectively (S801 and S802). The identification ofauthoritative anchor point servers for Users A and B may be achieved byusing some or all of the method described in connection with FIG. 7.

After the request is received at the authoritative anchor point servers216, the anchor point servers 216 will wait until an INVITE (or similarcall-setup request is received from either User A or User B). In theexample of FIG. 8, User A sends an INVITE to User B in an attempt toestablish a communication session (S803). The INVITE is initiallyreceived at the feature sequencer 224 and analyzed. The featuresequencer 224 checks to see which applications have requestednotifications for User A. In this example, the feature sequencer 224determines that application 208 has issued such a monitoring request forUser A and sends a notification to application 208 via the first anchorpoint server 216 a (S804). The first anchor point server 216 a sends anotification to application 208 that User A is calling User B (S805).After the application 208 has received the notification for User A, thenthe application 208 is ready to take some action on the communicationsession for User A. Since a notification has not yet been received forUser B, the application 208 will not yet be ready to take an action onthe communication session for User B.

Thereafter, the first anchor point server 216 a sends the INVITE back tothe feature sequencer 224 (S806). Upon re-receiving the INVITE, thefeature sequencer 224 checks its internally-maintained data structuresto determine which anchor point server is authoritative for User B andthen forwards the INVITE to the second anchor point server 216 b (S807).The second anchor point server 216 b checks to see which applicationshave requested notifications for User B and finds an entry indicatingthat application 208 has issued such a request for User B. Upon makingthis determination, the second anchor point server 216 b sends anotification to the application 208 (S808).

Thereafter, the second anchor point server 216 b sends the INVITE backto the feature sequencer 224 (S809), which subsequently sends the INVITEmessage to User B's endpoint (S810). Subsequent SIP messages used tofinalize establishment of the communication session may then beexchanged between endpoints and anchor point servers 216 a, 216 b in anormal Back-to-Back UA (B2BUA) fashion until a communication session isestablished between the endpoints.

With reference now to FIG. 9, a process of utilizing a CSID to enable anapplication 208 to operate on behalf of multiple users for acommunication session will be described in accordance with embodimentsof the present disclosure. As noted above, when a communication sessionis established, the communication session may be assigned a unique CSID.The CSID may be assigned to the communication session for the durationof the communication session. Upon termination of the communicationsession, the CSID may be returned to a CSID repository where it can beassigned to another communication session at a later point in time.While the CSID is assigned to a particular communication session, eachanchor point server 216 that is involved in the communication session(e.g., by having established one or more anchor points in theapplication sequence of that communication session) may be notified ofthe CSID and the CSID used by each anchor point server 216 to refer tothe communication session may be the same across all anchor pointservers 216.

In some embodiments, it is desirable for an application 208 to refer tothe communication session that it wants to control or be bound to ratherthan referring to a user that is involved in the communication session.Requests which reference a CSID rather than a user are generallydesirable in situations where the application 208 is issuing the requestfor all participants in a call or to add a user to an in-progress call.In these cases, the request is still directed to an anchor point server216 that has an anchor point and a call model for the communicationsession corresponding to the CSID as described above. If the request isinitially directed to an anchor point server 216 that hasn't establishedan anchor point in the communication session, then that anchor pointserver 216 may either query other anchor point servers 216 or refer toits internally-maintained lists 220 a, 220 b to discover which anchorpoint server 216 is authoritative for the requested CSID and willredirect the application 208 to that anchor point server 216. Thisprevents the anchor point servers 216 from having to share any per-calldata on an ongoing basis.

The method of utilizing a CSID rather than a user-based request startswith an application 208 receiving a request from a user to either issuea query for all participants in a call, add the user to an in-progresscall, or perform some other function that requires a reference to thecommunication session itself rather than a reference to a particularuser (step 904). In response to receiving the request, the application208 attempts to determine the CSID that has been assigned to thecommunication session (step 908). There are generally two ways in whichthe application 208 can obtain this CSID information: it can be informedof the CSID via a communication event when it is monitoring a user or itcan query for all calls that a given user is involved in. The CSID issomething that the application 208 is responsible for tracking ratherthan the client library 212; however, client library 212 and not theapplication 208 will track the association between a CSID and an anchorpoint server 216.

The application 208 then provides the client library 212 with the CSID,which causes the client library 212 to attempt to identify an anchorpoint server 216 that is authoritative for that CSID (step 912). If thisinformation is not known to the client library 212, then the clientlibrary 212 may send a request to one of the anchor point servers 216 inhopes that it either is or knows of the anchor point server 216 that isauthoritative for the CSID. Alternatively, the client library 212 mayidentify users that are associated with that CSID by referencing itslocally-maintained mappings as this information may be used to identifyan anchor point server 216 that is authoritative for the CSID.

The application 208 and client library 212 then work through the processdescribed with respect to FIGS. 7 and/or 8 and the application 208 iseventually bound to the communication session via the appropriate anchorpoint server(s) 216. Thereafter, the application 208 is capable ofexerting control over the communication session on behalf of multipleusers involved in the communication session (step 916). In particular,the application 208 may be allowed to leverage an anchor pointestablished by the anchor point server 216 to exert call and mediacontrol over the communication session.

In the foregoing description, for the purposes of illustration, methodswere described in a particular order. It should be appreciated that inalternate embodiments, the methods and steps thereof may be performed ina different order than that described. It should also be appreciatedthat the methods described above may be performed by hardware componentsor may be embodied in sequences of machine-executable instructions,which may be used to cause a machine, such as a general-purpose orspecial-purpose processor or logic circuits programmed with theinstructions to perform the methods. These machine-executableinstructions may be stored on one or more machine readable mediums, suchas CD-ROMs or other type of optical disks, floppy diskettes, ROMs, RAMs,EPROMs, EEPROMs, magnetic or optical cards, flash memory, or other typesof machine-readable mediums suitable for storing electronicinstructions. Alternatively, the methods may be performed by acombination of hardware and software.

Specific details were given in the description to provide a thoroughunderstanding of the embodiments. However, it will be understood by oneof ordinary skill in the art that the embodiments may be practicedwithout these specific details. For example, circuits may be shown inblock diagrams in order not to obscure the embodiments in unnecessarydetail. In other instances, well-known circuits, processes, algorithms,structures, and techniques may be shown without unnecessary detail inorder to avoid obscuring the embodiments.

Also, it is noted that the embodiments were described as a process whichis depicted as a flowchart, a flow diagram, a data flow diagram, astructure diagram, or a block diagram. Although a flowchart may describethe operations as a sequential process, many of the operations can beperformed in parallel or concurrently. In addition, the order of theoperations may be re-arranged. A process is terminated when itsoperations are completed, but could have additional steps not includedin the figure. A process may correspond to a method, a function, aprocedure, a subroutine, a subprogram, etc. When a process correspondsto a function, its termination corresponds to a return of the functionto the calling function or the main function.

Furthermore, embodiments may be implemented by hardware, software,firmware, middleware, microcode, hardware description languages, or anycombination thereof. When implemented in software, firmware, middlewareor microcode, the program code or code segments to perform the necessarytasks may be stored in a machine readable medium such as storage medium.A processor(s) may perform the necessary tasks. A code segment mayrepresent a procedure, a function, a subprogram, a program, a routine, asubroutine, a module, a software package, a class, or any combination ofinstructions, data structures, or program statements. A code segment maybe coupled to another code segment or a hardware circuit by passingand/or receiving information, data, arguments, parameters, or memorycontents. Information, arguments, parameters, data, etc. may be passed,forwarded, or transmitted via any suitable means including memorysharing, message passing, token passing, network transmission, etc.

While illustrative embodiments of the disclosure have been described indetail herein, it is to be understood that the inventive concepts may beotherwise variously embodied and employed, and that the appended claimsare intended to be construed to include such variations, except aslimited by the prior art.

What is claimed is:
 1. A method, comprising: receiving, at anapplication, a request to monitor and control communication sessions fora user; transmitting, by the application to one or more anchor pointservers, a request to receive event information for the user'scommunication sessions from the one or more anchor point servers;determining an identity of a first anchor point server that willestablish an anchor point in at least some of the user's communicationsessions; establishing a communication link between the application andfirst anchor point server such that the application can receive eventinformation about the user's communication sessions via thecommunication link; allowing the application to control at least some ofthe user's communication sessions via the first anchor point server;wherein the first anchor point server is authoritative for a first userthat issued the request received at the application and wherein theidentity of the first anchor point is determined by a client library,the client library servicing a plurality of applications; and updating adata entry in the client library to reflect that the first anchor pointserver is authoritative for the first user.
 2. The method of claim 1,wherein the first anchor point server is authoritative for thecommunication session and maintains exclusive control with respect toother anchor point servers over a Communication Session ID assigned tothe communication session.
 3. A method, comprising: receiving, at anapplication, a request to monitor and control communication sessions fora user; transmitting, by the application to one or more anchor pointservers, a request to receive event information for the user'scommunication sessions from the anchor point server; determining anidentity of a first anchor point server that will establish an anchorpoint in at least some of the user's communication sessions;establishing a communication link between the application and firstanchor point server such that the application can receive eventinformation about the user's communication sessions via thecommunication link; allowing the application to control at least some ofthe user's communication sessions via the first anchor point server; andwherein the first anchor point server receives event information aboutthe communication session from a conference focus and wherein the firstanchor point server composes a complete roster list for the conference.4. The method of claim 3, wherein the conference focus comprises aconference mixer that is mixing three or more media streams from threeor more endpoints engaged in the communication session.
 5. The method ofclaim 1, wherein the application is allowed to control all of the user'scommunication sessions via the first anchor point server as long as thefirst anchor point server is active.
 6. A non-transitory computerreadable medium having stored thereon instructions that cause anapplication server containing the computer readable medium to execute amethod, the instructions comprising: instructions configured to receiveand analyze a request to exert call and/or media control over acommunication session for a first user; instructions configured totransmit, to one or more anchor point servers, a request to receiveevent information about the communication session from the one or moreanchor point servers; instructions configured to determine an identityof a first anchor point server that has already established or willestablish an anchor point in the communication session for the firstuser; instructions configured to establish a communication link with thefirst anchor point server such that the application server can at leastone of transmit control signals for the communication session via thecommunication link and receive event information about communicationsession via the communication link; and wherein the first anchor pointserver is authoritative for the first user; and wherein the instructionsfurther comprise instructions configured to update a client librarymaintained at the application server to reflect that the first anchorpoint server is authoritative for the first user.
 7. The non-transitorycomputer readable medium of claim 6, wherein the client library isshared by a plurality of applications and maintains a local datastructure which maps users to authoritative anchor point servers.
 8. Thenon-transitory computer readable medium of claim 6, wherein the firstanchor point server is authoritative for the communication session andmaintains exclusive control with respect to other anchor point serversover a Communication Session ID assigned to the communication session.9. The non-transitory computer readable medium of claim 6, wherein thecommunication session is already established when the request istransmitted.
 10. The non-transitory computer readable medium of claim 6,wherein the communication session is not already established when therequest is transmitted.
 11. A communication system, comprising: a firstanchor point server configured to establish at least a first anchorpoint in one or more communication sessions; a second anchor pointserver configured to establish at least a second anchor point in one ormore communication sessions; an application executed on an applicationserver, the application configured to utilize one or both of the firstand second anchor point servers to exert at least one of call and mediacontrol over a communication session; wherein the first anchor pointserver is authoritative for a first user that issued a request receivedat the application and wherein the identity of the first anchor point isdetermined by a client library, the client library servicing a pluralityof applications; and updating a data entry in the client library toreflect that the first anchor point server is authoritative for thefirst user.
 12. The system of claim 11, wherein the second anchor pointserver is authoritative for a second user.
 13. The system of claim 12,wherein a mapping of the first anchor point server to the first user anda mapping of the second anchor point server to the second user ismaintained in the client library.
 14. The system of claim 11, whereinthe communication session is an in-progress communication session andwherein one or both of the first and second anchor point servers areutilized by the application to exert at least one of call and mediacontrol over the in-progress communication session when the applicationwas not initially sequenced into an application sequence duringinitialization of the communication session.
 15. The system of claim 11,wherein the application is initially bound to the communication sessionwhen at least one of the first and second anchor point servers aresequenced into the communication session.